Vaults are commonly used in banks and financial institutions to provide for safe reposit of money, documents and valuables. Many vault doors typically include a locking mechanism having two locks, which mechanism may be configured to open when one lock alone, or both locks together, are opened. A dual lock assembly which can be opened by opening one of the locks provides additional convenience in the event one lock fails by allowing access to the vault through use of the other lock; but does not provide additional security over a single lock assembly with respect to unauthorized entry into the vault. A dual lock assembly configured to require both locks be opened to open the assembly provides the additional security not provided by the foregoing one lock arrangement, but creates a problem in that if one of the locks fail, access to the vault is denied. For this reason vaults with doors utilizing a dual locking mechanism that require both locks be open sometimes also include a small emergency access opening (emergency door) in some inconvenient, not easily accessible section of the vault to permit access in the event of a lock failure. As can be appreciated, this feature detracts from the security of the vault.
It is also known to provide vault doors with locking mechanisms which include four locks. Such four lock mechanisms are commonly used in Federal Reserve Banks for additional security. The four locks are mechanically arranged such that opening any two of the locks will open the vault door. With such an arrangement, if one or two of the four locks fails, the vault can still be opened, since the remaining two locks can be opened. One of the problems with the four-lock arrangement is that it is complex and relatively expensive to build. Another problem is that the arrangement lacks versatility because the locks function in only one manner to open the vault door.
Further, none of the aforementioned lock assemblies provides an assembly for use in a situation wherein it may be desirable for security reasons to have a dual lock arrangement that requires two separate locks on a vault door be opened (preferably by two separate individuals) to gain access to a vault, but at the same time allows access to the vault to a single individual, such as an employer or supervisor, by opening a single lock.
The present invention overcomes these and other problems and provides a three-lock assembly for a security door, which lock assembly has a first configuration wherein unlocking any two of the locks will unlock the assembly, and a second configuration wherein two specific locks of the three locks must be unlocked to unlock the assembly, the remaining lock being a master lock and alone able to unlock the assembly.